1. Field of the Invention
The present invention relates to a fastener. When the fastener is inserted in a piece of material, at least one prong digs into the surface of the material to prevent the fastener from rotating when a threaded fastener is screwed into the fastener.
2. Description of Background Art
Fasteners including a flange with a shaft extending therefrom are well known. It is also well known to provide the shaft with an end remote from the flange having a reduced wall thickness to facilitate riveting that end over the surface of a piece of material through which the shaft has been inserted to hold the fastener against axial movement once riveted. Rivets may also prevent rotation of the fastener, particularly rivets which have alternating flaired and non-flaired portions.
However, riveting fasteners, which would be desirable to prevent rotation of the fasteners, is difficult in several situations, including the following:
1. Tapered holes. In the manufacture of office seating, the curved plywood pieces that make up the backs of the seats are sometimes punched out of a formed blank with a knife edge die. For forms with a simple curvature, this is faster than using a router to cut out the piece, and in addition the holes for the fasteners can be punched at the same time, saving the time and cost of the secondary drilling operation. However, punched holes are tapered. When using conventional riveting methods, it is difficult to ensure that there is sufficient penetration into the sides of the hole to prevent rotation when the hole is opening up.
2. Varying material thickness. Components made from plywood have a consistent thickness throughout. However components that are molded from plastic or a wood sawdust/resin mixture generally are thinner in some areas and thicker in others. This leads to different depths of holes into which the fasteners are inserted. It is very difficult to ensure consistently good riveting into different depth holes with a single set-up.
In view of the problems described above, a need has developed for a fastener that may be 1) guided within the track by the sides of the fastener; 2) more firmly secured to the surface of the material to prevent the fastener from rotating, particularly for fasteners that are not riveted; and 3) prevented from shingling solely by the thickness of the straight sides of the fastener. Furthermore, a need has developed for a fastener wherein the fastener blank is formed in a forging operation with the fastener blank being subsequently tapped. It is with these needs in mind that the present invention was developed.